Control apparatus



April 17, 1962 F. RASMUSSEN CONTROL APPARATUS Filed Dec. 6, 1960 FIG. I

States Patent Ofiice 3,629,792 Patented Apr. 17, 19t32 3,029,792- CONTROL APPARATUS Robert F. Rasmussen, Brooklyn Center, Minn.,. assiguor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Filed Dec. 6, 1960, Ser. No. 74,1552 7 Claims. (Cl; 121-58) This invention relates. to power actuators, and more particularly, to screw jack power actuators utilizing a compressible fluid such as air to'achieve an output force.

In the use of power actuators for high temperature applications, the effects of stagnation of the fluid in the system has become a diflicult problem. Because the incoming fluid has been cooled and the actuator is located in anarea of much higher ambient. temperature, it is obvious that the actuator must have a. displacement as small as possible in order to; insure: flushing? of the actuator with fresh cool fiuidwhen it is operated over comparably short strokes. This situation is doubly important in pneumatic systems, wherethe compressibility is dependent to such an extent on thevolume of modulated gas. Screw jack actuators have been considered for these high temperature amplifications, but the big draw back has always been the ever presence of backlash in. a'screw and nut.

These problems of stagnation and backlash are eliminated by the instant invention, which isbasically a radial piston motor operating a screw jack with balls serving both as pistons and as threads of aballnut. The radial piston motor differs from convention in that the pistons are loaded against the screw jack or threaded shaft, which-is eccentric to the cylinder thereof, instead of to the conventional outer race. In addition, the in stant invention utilizes a very small volume of compressed fiuid to-drive a threaded'rod or shaft by rotating the spherical or ball-type pistons in the threads of the shaft.

It is therefore an object of this invention to provide an improved control apparatus A further object of the invention is to provide an improved fluid. operated actuator that is of relatively simple construction and low in cost, and which eliminates the effects of fluid stagnation and backlash in high temperature actuators.

These and other objects of my invention will become apparent from the following description of a preferred form thereof, and the single sheet of drawing illustrating the invention in which: 7

FIGURE 1 is. a sectional view of my. actuator taken along the section line AA shown in FIGURE 2; and

FIGURE 2 is a section view of the actuator taken along the section line B--B in FIGURE. 1.

With reference to FIGURES l and 2 I have showna base, or body, or housing member 10 having a cylindrical bore therethrough. A cylindrical drum, or insert, or barrel 30 is concentrically mounted within said bore 15 by bearing means 31 and 33 which are located therebetween. The bearing means 31 and 33 are. arranged to allow rotation of the barrel 3%) relative to the bore 15 and the housing 10, but to prevent longitudi'nal'movement of the barrel 30 relative to the bore and the housing. The body or housing It) is cut away along sections of the inner wall of the bore 15 to formpressure ports 13 and 14, which communicate with the supply and exhaust passages 11 and 12. The barrel 30 has a plurality of cylindrical radial openings 20, 22,, and 24, therein, which are equally spaced along a helical path around the periphery of the barrel 30; The openings 20, 22; and 24",

also communicate with the pressure ports 13' and 14" as barrel 30 rotates relative to housing 10:

A threaded shaft" 49, containing a helical thread or threads thereon is mounted eccentrically within the barrel 30 by mounting means 32 and 34 located at opposite ends" of the barrel 30. The mounting means 32 and 34' are formed with eccentrically located openings therein. which hold shaft 4'0 in the eccentric position shown, but at the same time allow longitudinal displacement of the shaft 49 relative to the barrel 30 and the housing 10. The mounting. means 32 and 34 sup port theishaft 40 in: a: manner so as to minimize the bending loads on the shaft. The amount of. eccentricity of the shaft 40 relative to the: barrel 30 and the housing 10 is'designated' by the symbol e. It should be noted, that. shaft 4tlis' prevented from rotating by pin 42 which is connected. to connector 41 and is positioned within recesses 43 and 4d ofmember 45. Member 45 is fixed relative to housing 10. However, pin 42 is in' slideable engagement with member '45 so that shafti lh is allowed to move longitudinally.

A plurality of spherical pistons or balls 21, 23, and 25-, of substantially the same diameter as the openings 20, 22", and: 245 are placed into the openings, one piston being placed in each opening. The pistons 21, 23, and 25, when positioned in their respective openings 2t, 22, and 24-engage the thread or threads of the shaftl ti. lt should bepointed out that although the three pistons 21, 2'3; and 25, in FIGURE 1 appear to be located in a common plane, they are actually longitudinally displaced along the shaftso asto rest in the thread at each point (referto FIGURE 2). Thus, it shall be understood that the. section line AA istaken in such a way that this illustrationv can be shown.

Theactuator' inFlGURE 2, shows two sets of pistons locatedlat: diametrically opposite positions with respect to the shaft 49*. It should be understood, however, that they would ordinarily be located at degree intervals about the periphery of the barrel 30 as shown in FIG- URE 1; they are shown at degree intervals in FIG- URE 2' merely for the sake of' clarity of illustration. It would, of course, be possible to provide such pistons at other intervals, such as for example, 90 intervals, and achieve successful operation of the actuator. Furthermore, successful operation would result in the pistons being located at 180 intervals, after barrel 30 has achieved suificient rotational momentum to carry one set of pistons from the exhaust port area to the pressure port area.

Operation In operation, a source of high pressure and a lowpressure return passage are connected to fluid passages 11 and. 12; high pressure in line 11 being efiective to cause one direction of movement of the shaft 40 and high pressure in passage 12 being effective to cause movement in the opposite direction. Assume, for purposes of describing the operation of this device, that a high pressure is received in line 11. The high pressure is effective to flow into pressure port 13 and thereby flow into opening 22 and force piston 23 against the shaft 40; Pressure port 14 communicates with pressure passage 12 which is-connected to a low pressure source, when pressure passage 11 is connected to a high pressure source. It should be noted that openings22,,24, and 20. are. equally spaced along a helical. path around barrel 3h which has a generally cylindrical shape and is concentrically mounted within the bore l5'of housing 1%. However, the center of the shaft 49 is eccentrically mounted by means of mounting means 32 and 34, an amount e relative to the center of cylinder barrel 36 and bore 15'. This" eccentric from rotating by pin 42 and member 45 a'spreviously explained:

Thus, when high pressure is directed into openings 22, it causes piston 23 to be forced against the shaft 40 along a line extending to the center of barrel 30; this line of force extends through a point below the center of the shaft 40 as shown in FIGURE 1 due to the eccentric mounting of the shaft. The piston 23 is thereby caused to rotate or roll in a counterclockwise direction along the thread or threads of shaft 40. In so moving, piston 23 carries barrel 30 in a counterclockwise direction, carrying pistons 25 and 21 in the same direction. As opening 22 reaches the end of pressure port 13, opening 20 is exposed to the high pressure in pressure port 13, and the piston 21 is, in turn, driven in a counterclockwise direction along the threaded shaft 40. When opening 22 and piston 23 reach the pressure port 14, piston 23 is forced radially outward because of the eccentricity of shaft 40 and the pressure in opening 22 is then exhausted through exhaust pressure port 14 and exhaust passage 12. Thus, each piston is in turn, acted upon by the high pressure and is forced to move in a counterclockwise direction. In the above example, it is important to note that barrel 30 is prevented from moving in a longitudinal direction, and therefore in order for the pistons to remain in the threads or thread of the shaft 40, shaft 40 must move longitudinally within the barrel 30. The movement of the shaft 40 may be best understood by reference to FIGURE 2 and the following description.

In the embodiment illustrated in FIGURE 2, when high pressure exists in pressure port 13, each of the pistons 23, 27, and 35, is driven into its respective opening, 22, 26, and 36, and against the thread or threads of the shaft 40. As mentioned previously, the force of the pistons against the eccentrically mounted shaft 40 causes the pistons 23, 27 and 35 to rotate in a counterclockwise direction or out of the plane of the drawing as viewed in FIGURE 2. It is apparent then, that shaft 40 must move in a downward direction, as viewed in FIGURE 2, as the pistons cause the barrel 30 to rotate in a counterclockwise direction or out of the plane of the drawings. At the same time, pistons 25, 29 and 37 move radially outward in their respective openings 24, 28 and 38, so as to drive any fluid trapped therein out the exhaust pressure port 14 in the exhaust passage 12.

In a manner similar to that just described, it is obvious that a high pressure in the passage 12 and the pressure port 14, with exhaust pressures existing in pressure port 13, will cause an upward movement of shaft 40.

What has been described is considered to be the preferred embodiment of my invention, but it is apparent that numerous modifications thereof are possible, and that the concepts involved are not necessarily limited to penumatic operations. For example the hydraulic fluid could successfully be used in place of the pneumatic source of supply. Therefore, I do not wish to be limited to the form shown, except as indicated by the following claims.

I claim:

1. In a reversible pneumatic actuator: a housing including a cylindrical bore therethrough; a hollow cylindrical barrel; bearing means for rotatably mounting said barrel within said bore and concentric therewith, said bearing means also preventing longitudinal movement of said barrel relative to said housing; said barrel having a plurality of radial cylindrical openings therethrough, said openings being equally spaced along a helical path around the periphery of said barrel; a non-rotatable threaded shaft; mounting means for eccentrically mounting said shaft within said barrel, said mounting means allowing longitudinal movement of said shaft relative to said barrel and said housing; a plurality of spherical pistons, one of said pistons being positioned in each of said openings and engaging the thread of said shaft; a low pressure port formed in said housing and adjacent to said barrel and communicating with at least a first of said pistons; and a high pressure port formed in said housing and adjacent to said barrel and communicating with at least a second of said pistons whereby a high pressure fluid may be directed through said high pressure port to force said second of said pistons against the thread of said shaft; said force being directed against said shaft along a line perpendicular to its longitudinal axis and spaced therefrom, said force causing said second of said pistons to rotate and be displaced along the thread of said shaft causing said barrel to rotate concentrically relative to said housing and eccentrically relative to said shaft and being effective to longitudinally displace said shaft in one direction relative to said barrel and said housing, the interchanging of said high pressure port and said low pressure port being effective to cause displacement of said shaft in the opposite direction, the rotation of said barrel also being effective to move said second of said pistons from said high pressure port to said low pressure port, said fluid being exhausted through said low pressure port, and the continued rotation of said barrel being effective to return said second of said pistons to said high pressure port to complete the cycle of operation.

2. In a reversible actuator: a housing including a cylindrical bore therethrough; a hollow cylindrical sleeve; bearing means for rotatably mounting said sleeve within said bore and concentric therewith, said bearing means also preventing longitudinal movement of said barrel relative to said housing; said barrel having a plurality of radial openings therethrough, said openings being equally spaced along a helical path around the periphery of said sleeve; a non-rotatable multiple threaded shaft; means for eccentrically mounting said shaft within said sleeve, said mounting means allowing longitudinal movement of said shaft relative to said sleeve and said housing; a plurality of spherical pistons, one piston being positioned in each of said openings and engaging the thread of said shaft; a first pressure port formed in said housing and adjacent to said sleeve and communicating with at least one of said openings; and a second pressure port formed in said housing and adjacent to said sleeve and communicating with at least another of said openings whereby a high pressure fluid may be directed through said second pressure port to force at least one of said pistons against the thread of said shaft; said force being directed against said shaft along a line perpendicular to its longitudinal axis and spaced therefrom and causing said one of said pistons to be displaced along the threads of said shaft, the displacement of said one of said pistons causing said sleeve to rotate concentrically relative to said housing and eccentrically relative to said shaft and causing said shaft to be displaced in one direction along its longitudinal axis relative to said sleeve and said housing, the rotation of said sleeve also being effective to move said one of said pistons from said second pressure port to said first pressure port, said fluid being exhausted through said first pressure port, continued rotation of said barrel being effective to return said one of said pistons to said second pressure port to complete the cycle of operation, and the interchanging of said first and said second pressure ports being effective to cause displacement of said shaft in the opposite direction.

3. In a reversible actuator: a housing including a bore therethrough; a hollow cylindrical drum; bearing means for rotatably and concentrically mounting said barrel within said bore and preventing longitudinal movement of said drum relative to said housing; said barrel having a plurality of radial cylindrical openings therethrough, said openings being equally spaced along a helical path around the periphery of said drum; a non-rotatable threaded shaft; means for eccentrically mounting said shaft within said sleeve and allowing longitudinal movement of said shaft relative to said drum; a plurality of balls, one ball being positioned in each of said openings and engaging the thread of said shaft; and a plurality of pressure ports formed in said housing and adjacent to said drum whereby a high pressure fluid may be directed through a first of said pressure poi-ts to force at least one of said balls against the thread of said shaft, said force being directed against said shaft along a line perpendicular to its longitudinal axis and spaced therefrom, said force causing said one of said balls to be displaced along the thread of said shaft causing said drum to rotate concentrically relative to said housing and eccentrically relative to said shaft, the rotation of said drum in one direction being effective to displace said shaft in one direction along its longitudinal axis relative to the drum and housing, the rotation of said drum in the opposite direc tion causing displacement of said shaft in the opposite direction, the rotation of said drum also being effective to move said one of said balls from said first pressure port to a second of said pressure ports, said fluid being exhausted through said second of said pressure ports, and continued rotation of said drum being effective to return said one of said balls to said first pressure port to complete the cycle of operation.

4. In an actuator: a housing including a bore therethrough; a hollow barrel; bearing means for rotatably mounting said barrel concentrically within said bore and preventing longitudinal movement therebetween; said barrel having a total plurality of radial openings therethrough, said openings being spaced along a helical path around said barrel; a non-rotatable threaded shaft; means for eccentrically mounting said shaft within said sleeve and allowing reciprocal movement therebetween; a total plurality of pistons, one of said pistons being positioned in each of said openings and engaging the thread of said shaft; a high pressure port formed in said housing and adjacent to said barrel and communicating with a first plurality of said openings; and a low pressure port formed in said housing and adjacent to said barrel and communicating with a second plurality of said openings whereby a high pressure fluid may be directed through said high pressure port to force a first plurality of said pistons against the thread of said shaft; said force being directed against said shaft along a line perpendicular to its longitudinal axis and spaced therefrom, said force causing said first plurality of pistons to be displaced along the thread of said shaft causing said barrel to rotate concentrically relative to said housing and eccentrically relative to said shaft, the rotation of said barrel being effective to displace said shaft in one direction along its longitudinal axis relative to the drum and housing, the rotation of said barrel also being effective to move said first plurality of pistons from said high pressure port to said low pressure port, said fluid being exhausted through said low pressure port, and continued rotation of said barrel being effective to return said first plurality of pistons to said high pressure port to complete the cycle of operation.

5. In an actuator; a housing including a cylindrical oore therethrough; a hollow cylindrical drum; mounting means for rotatably mounting said drum within said bore and concentric therewith, said mounting means preventing longitudinal movement of said drum relative to said housing; said drum having a plurality of radial openings therethrough, said openings being equally spaced along a helical path around the periphery of saidvdrum; a nonrotatable threaded shaft; means for eccentrically mounting said shaft within said drum and permitting axial movement of said shaft relative to said drum; a plurality of pistons, one of said pistons being positioned within each of said openings and engaging the thread of said shaft;

means for supplying a high pressure fluid to at least one of said openings whereby said high pressure fluid may be directed against at least one of said pistons to force said pistons against said shaft causing rotation of said drum, the rotation of said drum causing said shaft to be displaced along its longitudinal axis relative to said drum; and means for exhausting said fluid after rotation of said drum.

6. In a radial piston motor; a housing having a bore therethrough; a hollow sleeve; means for rotatably and concentrically mounting said sleeve within said bore and preventing longitudinal movement thereof; said sleeve having a plurality of radial openings therethrough, said openings being spaced along a helical path around said sleeve; a non-rotatable threaded shaft; means for eccentrically mounting said shaft within said sleeve and allowing longitudinal movement therebetween; a plurality of pistons, one piston being positioned in each of said openings and engaging the thread of said shaft; and means for directing a high pressure fluid against at least one of said pistons whereby said one of said pistons may be displaced along the thread of said shaft causing rotation of said sleeve, the rotation of said sleeve causing longitudinal displacement of said shaft relative to said sleeve and said housing, and means for exhausting said high pressure fluid.

7. In combination: a housing having a bore therethrough; a hollow insert; means for rotatably mounting said insert concentrically Within said bore; said insert having a plurality of radial openings therethrough, said openings being spaced along a helical path around said insert; a plurality of pistons; a non-rotatable threaded shaft; means for eccentrically mounting said shaft within said insert and allowing axial movement therebetween; one of said pistons being positioned within each of said openings and engaging the thread of said shaft; means for directing a high pressure fluid against at least one of said pistons thereby forcing it against said shaft; the force of said piston against said eccentrically mounted shaft causing rotation of said insert, the rotation of said insert causing axial displacement of said shaft relative to said insert and said housing; and means for exhausting said fluid.

References Cited in the file of this patent UNITED STATES PATENTS 2,791,128 Geyer et a1. May 7, 1957 2,945,387 Geyer July 19, 1960 2,959,064 Geyer et al. Nov. 8, 1960 

